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, Available online 21 March 2024,
https://doi.org/10.1007/s12613-024-2889-5
Abstract:
Anterior cruciate ligament (ACL) injuries of the knee are one of the most common and serious athletic injuries. The widely used cortical suspension fixation buttons for ligament reconstruction are permanent implants, particularly those made from conventional steel or titanium alloys. In this study, a biodegradable Zn–0.45Mn–0.2Mg (ZMM42) alloy with the yield strength of 300.4 MPa and tensile strength of 329.8 MPa was prepared through hot extrusion. The use of zinc alloys in the preparation of cortical suspension fixation buttons was proposed for the first time. After 35 d of immersion in simulated body fluids, the ZMM42 alloy fixation buttons were degraded at a rate of 44 μm/a, and the fixation strength was retained (379.55 N) in the traction loops. Simultaneously, the ZMM42 alloy fixation buttons exhibited an increase in MC3T3-E1 cell viability and high antibacterial activity against Escherichia coli and Staphylococcus aureus. These results reveal the potential of biodegradable zinc alloys for use as ligament reconstruction materials and for developing diverse zinc alloy cortical suspension fixation devices.
Anterior cruciate ligament (ACL) injuries of the knee are one of the most common and serious athletic injuries. The widely used cortical suspension fixation buttons for ligament reconstruction are permanent implants, particularly those made from conventional steel or titanium alloys. In this study, a biodegradable Zn–0.45Mn–0.2Mg (ZMM42) alloy with the yield strength of 300.4 MPa and tensile strength of 329.8 MPa was prepared through hot extrusion. The use of zinc alloys in the preparation of cortical suspension fixation buttons was proposed for the first time. After 35 d of immersion in simulated body fluids, the ZMM42 alloy fixation buttons were degraded at a rate of 44 μm/a, and the fixation strength was retained (379.55 N) in the traction loops. Simultaneously, the ZMM42 alloy fixation buttons exhibited an increase in MC3T3-E1 cell viability and high antibacterial activity against Escherichia coli and Staphylococcus aureus. These results reveal the potential of biodegradable zinc alloys for use as ligament reconstruction materials and for developing diverse zinc alloy cortical suspension fixation devices.
, Available online 15 March 2024,
https://doi.org/10.1007/s12613-024-2881-0
Abstract:
Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness. In this study, KOH was evenly distributed on biomass Tremella using the swelling induction method, leading to the preparation of a three-dimensional network-structured hierarchical porous carbon (HPC) through carbonization. The achieved microwave absorption intensity is robust at −47.34 dB with a thin thickness of 2.1 mm. Notably, the widest effective absorption bandwidth, reaching 7.0 GHz (11–18 GHz), is attained at a matching thickness of 2.2 mm. The exceptional broadband and reflection loss performance are attributed to the 3D porous networks, interface effects, carbon network defects, and dipole relaxation. HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant. The uniform pore structures considerably optimize the impedance-matching performance of the material, while the abundance of interfaces and defects enhances the dielectric loss, thereby improving the attenuation constant. Furthermore, the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated. This research presents a strategy for preparing absorbing materials using biomass-derived HPC, showcasing considerable potential in the field of electromagnetic wave absorption.
Bioderived carbon materials have garnered considerable interest in the fields of microwave absorption and shielding due to their reproducibility and environmental friendliness. In this study, KOH was evenly distributed on biomass Tremella using the swelling induction method, leading to the preparation of a three-dimensional network-structured hierarchical porous carbon (HPC) through carbonization. The achieved microwave absorption intensity is robust at −47.34 dB with a thin thickness of 2.1 mm. Notably, the widest effective absorption bandwidth, reaching 7.0 GHz (11–18 GHz), is attained at a matching thickness of 2.2 mm. The exceptional broadband and reflection loss performance are attributed to the 3D porous networks, interface effects, carbon network defects, and dipole relaxation. HPC has outstanding absorption characteristics due to its excellent impedance matching and high attenuation constant. The uniform pore structures considerably optimize the impedance-matching performance of the material, while the abundance of interfaces and defects enhances the dielectric loss, thereby improving the attenuation constant. Furthermore, the impact of carbonization temperature and swelling rate on microwave absorption performance was systematically investigated. This research presents a strategy for preparing absorbing materials using biomass-derived HPC, showcasing considerable potential in the field of electromagnetic wave absorption.
, Available online 28 February 2024,
https://doi.org/10.1007/s12613-024-2870-3
Abstract:
Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process, high mechanical and electrical comprehensive performances, and low cost; thus, they are widely used in high-speed rail contact wires, electronic component connectors, and other devices. Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys. Taking the typical solid solution-strengthened alloy Cu–4Zn–1Sn as the research object, we proposed using the element In to replace Zn and Sn to achieve low alloying in this work. Two new alloys, Cu–1.5Zn–1Sn–0.4In and Cu–1.5Zn–0.9Sn–0.6In, were designed and prepared. The total weight percentage content of alloying elements decreased by 43% and 41%, respectively, while the product of ultimate tensile strength (UTS) and electrical conductivity (EC) of the annealed state increased by 14% and 15%. After cold rolling with a 90% reduction, the UTS of the two new alloys reached 576 and 627 MPa, respectively, the EC was 44.9%IACS and 42.0%IACS, and the product of UTS and EC (UTS × EC) was 97% and 99% higher than that of the annealed state alloy. The dislocations proliferated greatly in cold-rolled alloys, and the strengthening effects of dislocations reached 332 and 356 MPa, respectively, which is the main reason for the considerable improvement in mechanical properties.
Solid solution-strengthened copper alloys have the advantages of a simple composition and manufacturing process, high mechanical and electrical comprehensive performances, and low cost; thus, they are widely used in high-speed rail contact wires, electronic component connectors, and other devices. Overcoming the contradiction between low alloying and high performance is an important challenge in the development of solid solution-strengthened copper alloys. Taking the typical solid solution-strengthened alloy Cu–4Zn–1Sn as the research object, we proposed using the element In to replace Zn and Sn to achieve low alloying in this work. Two new alloys, Cu–1.5Zn–1Sn–0.4In and Cu–1.5Zn–0.9Sn–0.6In, were designed and prepared. The total weight percentage content of alloying elements decreased by 43% and 41%, respectively, while the product of ultimate tensile strength (UTS) and electrical conductivity (EC) of the annealed state increased by 14% and 15%. After cold rolling with a 90% reduction, the UTS of the two new alloys reached 576 and 627 MPa, respectively, the EC was 44.9%IACS and 42.0%IACS, and the product of UTS and EC (UTS × EC) was 97% and 99% higher than that of the annealed state alloy. The dislocations proliferated greatly in cold-rolled alloys, and the strengthening effects of dislocations reached 332 and 356 MPa, respectively, which is the main reason for the considerable improvement in mechanical properties.
, Available online 17 January 2024,
https://doi.org/10.1007/s12613-024-2832-9
Abstract:
Cemented paste backfill (CPB) is a key technology for green mining in metal mines, in which tailings thickening comprises the primary link of CPB technology. However, difficult flocculation and substandard concentrations of thickened tailings often occur. The rheological properties and concentration evolution in the thickened tailings remain unclear. Moreover, traditional indoor thickening experiments have yet to quantitatively characterize their rheological properties. An experiment of flocculation condition optimization based on the Box–Behnken design (BBD) was performed in the study, and the two response values were investigated: concentration and the mean weighted chord length (MWCL) of flocs. Thus, optimal flocculation conditions were obtained. In addition, the rheological properties and concentration evolution of different flocculant dosages and ultrafine tailing contents under shear, compression, and compression–shear coupling experimental conditions were tested and compared. The results show that the shear yield stress under compression and compression–shear coupling increases with the growth of compressive yield stress, while the shear yield stress increases slightly under shear. The order of shear yield stress from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Under compression and compression–shear coupling, the concentration first rapidly increases with the growth of compressive yield stress and then slowly increases, while concentration increases slightly under shear. The order of concentration from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Finally, the evolution mechanism of the flocs and drainage channels during the thickening of the thickened tailings under different experimental conditions was revealed.
Cemented paste backfill (CPB) is a key technology for green mining in metal mines, in which tailings thickening comprises the primary link of CPB technology. However, difficult flocculation and substandard concentrations of thickened tailings often occur. The rheological properties and concentration evolution in the thickened tailings remain unclear. Moreover, traditional indoor thickening experiments have yet to quantitatively characterize their rheological properties. An experiment of flocculation condition optimization based on the Box–Behnken design (BBD) was performed in the study, and the two response values were investigated: concentration and the mean weighted chord length (MWCL) of flocs. Thus, optimal flocculation conditions were obtained. In addition, the rheological properties and concentration evolution of different flocculant dosages and ultrafine tailing contents under shear, compression, and compression–shear coupling experimental conditions were tested and compared. The results show that the shear yield stress under compression and compression–shear coupling increases with the growth of compressive yield stress, while the shear yield stress increases slightly under shear. The order of shear yield stress from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Under compression and compression–shear coupling, the concentration first rapidly increases with the growth of compressive yield stress and then slowly increases, while concentration increases slightly under shear. The order of concentration from low to high under different thickening conditions is shear, compression, and compression–shear coupling. Finally, the evolution mechanism of the flocs and drainage channels during the thickening of the thickened tailings under different experimental conditions was revealed.
, Available online 12 January 2024,
https://doi.org/10.1007/s12613-024-2827-6
Abstract:
The nonproportional multiaxial ratchetting of cast AZ91 magnesium (Mg) alloy was examined by performing a sequence of axial–torsional cyclic tests controlled by stress with various loading paths at room temperature (RT). The evolutionary characteristics and path dependence of multiaxial ratchetting were discussed. Results illustrate that the cast AZ91 Mg alloy exhibits considerable nonproportional additional softening during cyclic loading with multiple nonproportional multiaxial loading paths; multiaxial ratchetting presents strong path dependence, and axial ratchetting strains are larger under nonproportional loading paths than under uniaxial and proportional 45° linear loading paths; multiaxial ratchetting becomes increasingly pronounced as the applied stress amplitude and axial mean stress increase. Moreover, stress–strain curves show a convex and symmetrical shape in axial/torsional directions. Multiaxial ratchetting exhibits quasi-shakedown after certain loading cycles. The abundant experimental data obtained in this work can be used to develop a cyclic plasticity model of cast Mg alloys.
The nonproportional multiaxial ratchetting of cast AZ91 magnesium (Mg) alloy was examined by performing a sequence of axial–torsional cyclic tests controlled by stress with various loading paths at room temperature (RT). The evolutionary characteristics and path dependence of multiaxial ratchetting were discussed. Results illustrate that the cast AZ91 Mg alloy exhibits considerable nonproportional additional softening during cyclic loading with multiple nonproportional multiaxial loading paths; multiaxial ratchetting presents strong path dependence, and axial ratchetting strains are larger under nonproportional loading paths than under uniaxial and proportional 45° linear loading paths; multiaxial ratchetting becomes increasingly pronounced as the applied stress amplitude and axial mean stress increase. Moreover, stress–strain curves show a convex and symmetrical shape in axial/torsional directions. Multiaxial ratchetting exhibits quasi-shakedown after certain loading cycles. The abundant experimental data obtained in this work can be used to develop a cyclic plasticity model of cast Mg alloys.
, Available online 3 January 2024,
https://doi.org/10.1007/s12613-024-2822-y
Abstract:
Structural instability in underground engineering, especially in coal–rock structures, poses significant safety risks. Thus, the development of an accurate monitoring method for the health of coal–rock bodies is crucial. The focus of this work is on understanding energy evolution patterns in coal–rock bodies under complex conditions by using shear, splitting, and uniaxial compression tests. We examine the changes in energy parameters during various loading stages and the effects of various failure modes, resulting in an innovative energy dissipation-based health evaluation technique for coal. Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading, indicated by fluctuations in elastic energy and dissipation energy density. For tensile failure, the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress. On the other hand, shear failure is described by “high accumulation and low dissipation” in energy trends. Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization, and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples. A novel mathematical and statistical approach is developed, establishing a dissipation energy anomaly index, W, which categorizes the structural health of coal into different danger levels. This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments, contributing to the development of structural health monitoring technology.
Structural instability in underground engineering, especially in coal–rock structures, poses significant safety risks. Thus, the development of an accurate monitoring method for the health of coal–rock bodies is crucial. The focus of this work is on understanding energy evolution patterns in coal–rock bodies under complex conditions by using shear, splitting, and uniaxial compression tests. We examine the changes in energy parameters during various loading stages and the effects of various failure modes, resulting in an innovative energy dissipation-based health evaluation technique for coal. Key results show that coal bodies go through transitions between strain hardening and softening mechanisms during loading, indicated by fluctuations in elastic energy and dissipation energy density. For tensile failure, the energy profile of coal shows a pattern of “high dissipation and low accumulation” before peak stress. On the other hand, shear failure is described by “high accumulation and low dissipation” in energy trends. Different failure modes correlate with an accelerated increase in the dissipation energy before destabilization, and a significant positive correlation is present between the energy dissipation rate and the stress state of the coal samples. A novel mathematical and statistical approach is developed, establishing a dissipation energy anomaly index, W, which categorizes the structural health of coal into different danger levels. This method provides a quantitative standard for early warning systems and is adaptable for monitoring structural health in complex underground engineering environments, contributing to the development of structural health monitoring technology.
, Available online 29 December 2023,
https://doi.org/10.1007/s12613-023-2821-4
Abstract:
This study introduces a coupled electromagnetic–thermal–mechanical model to reveal the mechanisms of microcracking and mineral melting of polymineralic rocks under microwave radiation. Experimental tests validate the rationality of the proposed model. Embedding microscopic mineral sections into the granite model for simulation shows that uneven temperature gradients create distinct molten, porous, and nonmolten zones on the fracture surface. Moreover, the varying thermal expansion coefficients and Young’s moduli among the minerals induce significant thermal stress at the mineral boundaries. Quartz and biotite with higher thermal expansion coefficients are subjected to compression, whereas plagioclase with smaller coefficients experiences tensile stress. In the molten zone, quartz undergoes transgranular cracking due to the α–β phase transition. The local high temperatures also induce melting phase transitions in biotite and feldspar. This numerical study provides new insights into the distribution of thermal stress and mineral phase changes in rocks under microwave irradiation.
This study introduces a coupled electromagnetic–thermal–mechanical model to reveal the mechanisms of microcracking and mineral melting of polymineralic rocks under microwave radiation. Experimental tests validate the rationality of the proposed model. Embedding microscopic mineral sections into the granite model for simulation shows that uneven temperature gradients create distinct molten, porous, and nonmolten zones on the fracture surface. Moreover, the varying thermal expansion coefficients and Young’s moduli among the minerals induce significant thermal stress at the mineral boundaries. Quartz and biotite with higher thermal expansion coefficients are subjected to compression, whereas plagioclase with smaller coefficients experiences tensile stress. In the molten zone, quartz undergoes transgranular cracking due to the α–β phase transition. The local high temperatures also induce melting phase transitions in biotite and feldspar. This numerical study provides new insights into the distribution of thermal stress and mineral phase changes in rocks under microwave irradiation.
, Available online 15 December 2023,
https://doi.org/10.1007/s12613-023-2810-7
Abstract:
Incorporating a selenium (Se) positive electrode into aluminum (Al)-ion batteries is an effective strategy for improving the overall battery performance. However, the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products. In this work, we aim to harness the advantages of Se while reducing its limitations by preparing a core–shell mesoporous carbon hollow sphere with a titanium nitride (C@TiN) host to load 63.9wt% Se as the positive electrode material for Al–Se batteries. Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN, the obtained core–shell mesoporous carbon hollow spheres coated with Se (Se@C@TiN) display superior utilization of the active material and remarkable cycling stability. As a result, Al–Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g−1 at a current density of 1000 mA·g−1 while maintaining a discharge specific capacity of 86.0 mAh·g−1 over 200 cycles. This improved cycling performance is ascribed to the high electrical conductivity of the core–shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.
Incorporating a selenium (Se) positive electrode into aluminum (Al)-ion batteries is an effective strategy for improving the overall battery performance. However, the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products. In this work, we aim to harness the advantages of Se while reducing its limitations by preparing a core–shell mesoporous carbon hollow sphere with a titanium nitride (C@TiN) host to load 63.9wt% Se as the positive electrode material for Al–Se batteries. Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN, the obtained core–shell mesoporous carbon hollow spheres coated with Se (Se@C@TiN) display superior utilization of the active material and remarkable cycling stability. As a result, Al–Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g−1 at a current density of 1000 mA·g−1 while maintaining a discharge specific capacity of 86.0 mAh·g−1 over 200 cycles. This improved cycling performance is ascribed to the high electrical conductivity of the core–shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.
, Available online 15 December 2023,
https://doi.org/10.1007/s12613-023-2812-5
Abstract:
The basal texture of traditional magnesium alloy AZ31 is easy to form and exhibits poor plasticity at room temperature. To address these problems, a multi-micro-alloyed high-plasticity Mg–1.8Zn–0.8Gd–0.1Ca–0.2Mn (wt%) alloy was developed using the unique role of rare earth and Ca solute atoms. In addition, the influence of the annealing process on the grain size, second phase, texture, and mechanical properties of the warm-rolled sheet at room temperature was analyzed with the goal of developing high-plasticity magnesium alloy sheets and obtaining optimal thermal-mechanical treatment parameters. The results show that the annealing temperature has a significant effect on the microstructure and properties due to the low alloying content: there are small amounts of larger-sized block and long string phases along the rolling direction, as well as several spherical and rodlike particle phases inside the grains. With increasing annealing temperature, the grain size decreases and then increases, and the morphology, number, and size of the second phase also change correspondingly. The particle phase within the grains vanishes at 450°C, and the grain size increases sharply. In the full recrystallization stage at 300–350°C, the optimum strength–plasticity comprehensive mechanical properties are presented, with yield strengths of 182.1 and 176.9 MPa, tensile strengths of 271.1 and 275.8 MPa in the RD and TD, and elongation values of 27.4% and 32.3%, respectively. Moreover, there are still some larger-sized phases in the alloy that influence its mechanical properties, which offers room for improvement.
The basal texture of traditional magnesium alloy AZ31 is easy to form and exhibits poor plasticity at room temperature. To address these problems, a multi-micro-alloyed high-plasticity Mg–1.8Zn–0.8Gd–0.1Ca–0.2Mn (wt%) alloy was developed using the unique role of rare earth and Ca solute atoms. In addition, the influence of the annealing process on the grain size, second phase, texture, and mechanical properties of the warm-rolled sheet at room temperature was analyzed with the goal of developing high-plasticity magnesium alloy sheets and obtaining optimal thermal-mechanical treatment parameters. The results show that the annealing temperature has a significant effect on the microstructure and properties due to the low alloying content: there are small amounts of larger-sized block and long string phases along the rolling direction, as well as several spherical and rodlike particle phases inside the grains. With increasing annealing temperature, the grain size decreases and then increases, and the morphology, number, and size of the second phase also change correspondingly. The particle phase within the grains vanishes at 450°C, and the grain size increases sharply. In the full recrystallization stage at 300–350°C, the optimum strength–plasticity comprehensive mechanical properties are presented, with yield strengths of 182.1 and 176.9 MPa, tensile strengths of 271.1 and 275.8 MPa in the RD and TD, and elongation values of 27.4% and 32.3%, respectively. Moreover, there are still some larger-sized phases in the alloy that influence its mechanical properties, which offers room for improvement.
, Available online 8 December 2023,
https://doi.org/10.1007/s12613-023-2805-4
Abstract:
Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels. In this work, the austenite dynamic recrystallization (DRX) behaviors of a eutectoid pearlite rail steel were studied using a thermo-mechanical simulator with hot deformation parameters frequently employed in rail production lines. The single-pass hot deformation results reveal that the prior austenite grain sizes (PAGSs) for samples with different deformation reductions decrease initially with an increase in deformation temperature. However, once the deformation temperature is beyond a certain threshold, the PAGSs start to increase. It can be attributed to the rise in DRX volume fraction and the increase of DRX grain with deformation temperature, respectively. Three-pass hot deformation results show that the accumulated strain generated in the first and second deformation passes can increase the extent of DRX. In the case of complete DRX, PAGS is predominantly determined by the deformation temperature of the final pass. It suggests a strategic approach during industrial production where part of the deformation reduction in low temperature range can be shifted to the medium temperature range to release rolling mill loads.
Understandings of the effect of hot deformation parameters close to the practical production line on grain refinement are crucial for enhancing both the strength and toughness of future rail steels. In this work, the austenite dynamic recrystallization (DRX) behaviors of a eutectoid pearlite rail steel were studied using a thermo-mechanical simulator with hot deformation parameters frequently employed in rail production lines. The single-pass hot deformation results reveal that the prior austenite grain sizes (PAGSs) for samples with different deformation reductions decrease initially with an increase in deformation temperature. However, once the deformation temperature is beyond a certain threshold, the PAGSs start to increase. It can be attributed to the rise in DRX volume fraction and the increase of DRX grain with deformation temperature, respectively. Three-pass hot deformation results show that the accumulated strain generated in the first and second deformation passes can increase the extent of DRX. In the case of complete DRX, PAGS is predominantly determined by the deformation temperature of the final pass. It suggests a strategic approach during industrial production where part of the deformation reduction in low temperature range can be shifted to the medium temperature range to release rolling mill loads.
, Available online 1 December 2023,
https://doi.org/10.1007/s12613-023-2801-8
Abstract:
This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hot-roll bonding (HRB) based on friction stir welding. The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum, and the tensile specimens fractured at the matrix after exceeding 1 Pa. Non-equilibrium grain boundaries were formed at the hot-rolled interface, and a large amount of Mg2Si particles were linearly precipitated along the interfacial grain boundaries (IGBs). During subsequent heat treatment, Mg2Si particles dissolved back into the matrix, and Al2O3 film remaining at the interface eventually evolved into MgO. In addition, the local IGBs underwent staged elimination during HRB, which facilitated the interface healing due to the fusion of grains at the interface. This process was achieved by the dissociation, emission, and annihilation of dislocations on the IGBs.
This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hot-roll bonding (HRB) based on friction stir welding. The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum, and the tensile specimens fractured at the matrix after exceeding 1 Pa. Non-equilibrium grain boundaries were formed at the hot-rolled interface, and a large amount of Mg2Si particles were linearly precipitated along the interfacial grain boundaries (IGBs). During subsequent heat treatment, Mg2Si particles dissolved back into the matrix, and Al2O3 film remaining at the interface eventually evolved into MgO. In addition, the local IGBs underwent staged elimination during HRB, which facilitated the interface healing due to the fusion of grains at the interface. This process was achieved by the dissociation, emission, and annihilation of dislocations on the IGBs.
, Available online 25 November 2023,
https://doi.org/10.1007/s12613-023-2793-4
Abstract:
Malachite is a common copper oxide mineral that is often enriched using the sulfidization–xanthate flotation method. Currently, the direct sulfidization method cannot yield copper concentrate products. Therefore, a new sulfidization flotation process was developed to promote the efficient recovery of malachite. In this study, Cu2+ was used as an activator to interact with the sample surface and increase its reaction sites, thereby strengthening the mineral sulfidization process and reactivity. Compared to single copper ion activation, the flotation effect of malachite significantly increased after stepwise Cu2+ activation. Zeta potential, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF–SIMS), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS), and atomic force microscopy (AFM) analysis results indicated that the adsorption of S species was significantly enhanced on the mineral surface due to the increase in active Cu sites after Cu2+ stepwise activation. Meanwhile, the proportion of active Cu–S species also increased, further improving the reaction between the sample surface and subsequent collectors. Fourier-transform infrared spectroscopy (FT-IR) and contact angle tests implied that the xanthate species were easily and stably adsorbed onto the mineral surface after Cu2+ stepwise activation, thereby improving the hydrophobicity of the mineral surface. Therefore, the copper sites on the malachite surface after Cu2+ stepwise activation promote the reactivity of the mineral surface and enhance sulfidization flotation of malachite.
Malachite is a common copper oxide mineral that is often enriched using the sulfidization–xanthate flotation method. Currently, the direct sulfidization method cannot yield copper concentrate products. Therefore, a new sulfidization flotation process was developed to promote the efficient recovery of malachite. In this study, Cu2+ was used as an activator to interact with the sample surface and increase its reaction sites, thereby strengthening the mineral sulfidization process and reactivity. Compared to single copper ion activation, the flotation effect of malachite significantly increased after stepwise Cu2+ activation. Zeta potential, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF–SIMS), scanning electron microscopy and energy dispersive spectrometry (SEM–EDS), and atomic force microscopy (AFM) analysis results indicated that the adsorption of S species was significantly enhanced on the mineral surface due to the increase in active Cu sites after Cu2+ stepwise activation. Meanwhile, the proportion of active Cu–S species also increased, further improving the reaction between the sample surface and subsequent collectors. Fourier-transform infrared spectroscopy (FT-IR) and contact angle tests implied that the xanthate species were easily and stably adsorbed onto the mineral surface after Cu2+ stepwise activation, thereby improving the hydrophobicity of the mineral surface. Therefore, the copper sites on the malachite surface after Cu2+ stepwise activation promote the reactivity of the mineral surface and enhance sulfidization flotation of malachite.
, Available online 21 November 2023,
https://doi.org/10.1007/s12613-023-2792-5
Abstract:
The microstructure characteristics and strengthening mechanism of Inconel738LC (IN-738LC) alloy prepared by using induction-assisted directed energy deposition (IDED) were elucidated through the investigation of samples subjected to IDED under 1050°C preheating with and without hot isostatic pressing (HIP, 1190°C, 105 MPa, and 3 h). Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ' phases in interdendritic and dendritic core regions. After HIP, grain morphology changed negligibly, whereas the size of the γ' phase became increasingly uneven. After further heat treatment (HT, 1070°C, 2 h + 845°C, 24 h), the γ' phase in the as-deposited and HIPed samples presented a bimodal size distribution, whereas that in the as-deposited sample showed a size that remained uneven. The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%, respectively, due to the synergistic deformation of bimodal γ' phases, especially large cubic γ' phases. Finally, the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.
The microstructure characteristics and strengthening mechanism of Inconel738LC (IN-738LC) alloy prepared by using induction-assisted directed energy deposition (IDED) were elucidated through the investigation of samples subjected to IDED under 1050°C preheating with and without hot isostatic pressing (HIP, 1190°C, 105 MPa, and 3 h). Results show that the as-deposited sample mainly consisted of epitaxial columnar crystals and inhomogeneously distributed γ' phases in interdendritic and dendritic core regions. After HIP, grain morphology changed negligibly, whereas the size of the γ' phase became increasingly uneven. After further heat treatment (HT, 1070°C, 2 h + 845°C, 24 h), the γ' phase in the as-deposited and HIPed samples presented a bimodal size distribution, whereas that in the as-deposited sample showed a size that remained uneven. The comparison of tensile properties revealed that the tensile strength and uniform elongation of the HIP + HTed sample increased by 5% and 46%, respectively, due to the synergistic deformation of bimodal γ' phases, especially large cubic γ' phases. Finally, the relationship between phase transformations and plastic deformations in the IDEDed sample was discussed on the basis of generalized stability theory in terms of the trade-off between thermodynamics and kinetics.
Research ArticleOpen Access
, Available online 10 November 2023,
https://doi.org/10.1007/s12613-023-2783-6
Abstract:
A critical challenge to the commercialization of clean and high-efficiency solid oxide fuel cell (SOFC) technology is the insufficient stack lifespan caused by a variety of degradation mechanisms, which are associated with cell components and chemical feedstocks. Cell components related degradation refers to thermal/chemical/electrochemical deterioration of cell materials under operating conditions, whereas the latter regards impurities in feedstocks of oxidant (air) and reductant (fuel). This article provides a thermodynamic perspective on the understanding of the impurities-induced degradation mechanisms in SOFCs. The discussion focuses on using thermodynamic analysis to elucidate poisoning mechanisms in cathodes by impurity species such as Cr, CO2, H2O, and SO2 and in the anode by species such as S (or H2S), SiO2, and P2 (or PH3). The author hopes the presented fundamental insights can provide a theoretical foundation for searching for better technical solutions to address the critical degradation challenges.
A critical challenge to the commercialization of clean and high-efficiency solid oxide fuel cell (SOFC) technology is the insufficient stack lifespan caused by a variety of degradation mechanisms, which are associated with cell components and chemical feedstocks. Cell components related degradation refers to thermal/chemical/electrochemical deterioration of cell materials under operating conditions, whereas the latter regards impurities in feedstocks of oxidant (air) and reductant (fuel). This article provides a thermodynamic perspective on the understanding of the impurities-induced degradation mechanisms in SOFCs. The discussion focuses on using thermodynamic analysis to elucidate poisoning mechanisms in cathodes by impurity species such as Cr, CO2, H2O, and SO2 and in the anode by species such as S (or H2S), SiO2, and P2 (or PH3). The author hopes the presented fundamental insights can provide a theoretical foundation for searching for better technical solutions to address the critical degradation challenges.
, Available online 10 November 2023,
https://doi.org/10.1007/s12613-023-2780-9
Abstract:
Controlling the content of athermal martensite and retained austenite is important to improving the mechanical properties of high-strength steels, but a mechanism for the accurate description of martensitic transformation during the cooling process must be addressed. At present, frequently used semi-empirical kinetics models suffer from huge errors at the beginning of transformation, and most of them fail to exhibit the sigmoidal shape characteristic of transformation curves. To describe the martensitic transformation process accurately, based on the Magee model, we introduced the changes in the nucleation activation energy of martensite with temperature, which led to the varying nucleation rates of this model during martensitic transformation. According to the calculation results, the relative error of the modified model for the martensitic transformation kinetics curves of Fe–C–X (X = Ni, Cr, Mn, Si) alloys reached 9.5% compared with those measured via the thermal expansion method. The relative error was approximately reduced by two-thirds compared with that of the Magee model. The incorporation of nucleation activation energy into the kinetics model contributes to the improvement of its precision.
Controlling the content of athermal martensite and retained austenite is important to improving the mechanical properties of high-strength steels, but a mechanism for the accurate description of martensitic transformation during the cooling process must be addressed. At present, frequently used semi-empirical kinetics models suffer from huge errors at the beginning of transformation, and most of them fail to exhibit the sigmoidal shape characteristic of transformation curves. To describe the martensitic transformation process accurately, based on the Magee model, we introduced the changes in the nucleation activation energy of martensite with temperature, which led to the varying nucleation rates of this model during martensitic transformation. According to the calculation results, the relative error of the modified model for the martensitic transformation kinetics curves of Fe–C–X (X = Ni, Cr, Mn, Si) alloys reached 9.5% compared with those measured via the thermal expansion method. The relative error was approximately reduced by two-thirds compared with that of the Magee model. The incorporation of nucleation activation energy into the kinetics model contributes to the improvement of its precision.
, Available online 25 October 2023,
https://doi.org/10.1007/s12613-023-2766-7
Abstract:
Herein, a thermodynamic model aimed at describing deoxidation equilibria in liquid steel was developed. The model provides explicit forms of the activity coefficient of solutes in liquid steel, eliminating the need for the minimization of internal Gibbs energy preliminarily when solving deoxidation equilibria. The elimination of internal Gibbs energy minimization is particularly advantageous during the coupling of deoxidation equilibrium calculations with computationally intensive approaches, such as computational fluid dynamics. The model enables efficient calculations through direct embedment of the explicit forms of activity coefficient in the computing code. The proposed thermodynamic model was developed using a quasichemical approach with two key approximations: random mixing of metallic elements (Fe and oxidizing metal) and strong nonrandom pairing of metal and oxygen as nearest neighbors. Through these approximations, the quasichemical approach yielded the activity coefficients of solutes as explicit functions of composition and temperature without requiring the minimization of internal Gibbs energy or the coupling of separate programs. The model was successfully applied in the calculation of deoxidation equilibria of various elements (Al, B, C, Ca, Ce, Cr, La, Mg, Mn, Nb, Si, Ti, V, and Zr). The limitations of the model arising from these assumptions were also discussed.
Herein, a thermodynamic model aimed at describing deoxidation equilibria in liquid steel was developed. The model provides explicit forms of the activity coefficient of solutes in liquid steel, eliminating the need for the minimization of internal Gibbs energy preliminarily when solving deoxidation equilibria. The elimination of internal Gibbs energy minimization is particularly advantageous during the coupling of deoxidation equilibrium calculations with computationally intensive approaches, such as computational fluid dynamics. The model enables efficient calculations through direct embedment of the explicit forms of activity coefficient in the computing code. The proposed thermodynamic model was developed using a quasichemical approach with two key approximations: random mixing of metallic elements (Fe and oxidizing metal) and strong nonrandom pairing of metal and oxygen as nearest neighbors. Through these approximations, the quasichemical approach yielded the activity coefficients of solutes as explicit functions of composition and temperature without requiring the minimization of internal Gibbs energy or the coupling of separate programs. The model was successfully applied in the calculation of deoxidation equilibria of various elements (Al, B, C, Ca, Ce, Cr, La, Mg, Mn, Nb, Si, Ti, V, and Zr). The limitations of the model arising from these assumptions were also discussed.
, Available online 13 October 2023,
https://doi.org/10.1007/s12613-023-2763-x
Abstract:
The interfacial wettability and heat transfer behavior are crucial in the strip casting of high phosphorus-containing steel. A high-temperature simulation of strip casting was conducted using the droplet solidification technique with the aims to reveal the effects of phosphorus content on interfacial wettability, deposited film, and interfacial heat transfer behavior. Results showed that when the phosphorus content increased from 0.014wt% to 0.406wt%, the mushy zone enlarged, the complete solidification temperature delayed from 1518.3 to 1459.4°C, the final contact angle decreased from 118.4° to 102.8°, indicating improved interfacial contact, and the maximum heat flux increased from 6.9 to 9.2 MW/m2. Increasing the phosphorus content from 0.081wt% to 0.406wt% also accelerated the film deposition rate from 1.57 to 1.73 μm per test, resulting in a thickened naturally deposited film with increased thermal resistance that advanced the transition point of heat transfer from the fifth experiment to the third experiment.
The interfacial wettability and heat transfer behavior are crucial in the strip casting of high phosphorus-containing steel. A high-temperature simulation of strip casting was conducted using the droplet solidification technique with the aims to reveal the effects of phosphorus content on interfacial wettability, deposited film, and interfacial heat transfer behavior. Results showed that when the phosphorus content increased from 0.014wt% to 0.406wt%, the mushy zone enlarged, the complete solidification temperature delayed from 1518.3 to 1459.4°C, the final contact angle decreased from 118.4° to 102.8°, indicating improved interfacial contact, and the maximum heat flux increased from 6.9 to 9.2 MW/m2. Increasing the phosphorus content from 0.081wt% to 0.406wt% also accelerated the film deposition rate from 1.57 to 1.73 μm per test, resulting in a thickened naturally deposited film with increased thermal resistance that advanced the transition point of heat transfer from the fifth experiment to the third experiment.
, Available online 12 October 2023,
https://doi.org/10.1007/s12613-023-2757-8
Abstract:
Te treatment is an effective method for modifying sulfide inclusions, and MnTe precipitation has an important effect on thermal brittleness and steel corrosion resistance. In most actual industrial applications of Te treatment, MnTe precipitation is unexpected. The critical precipitation behavior of MnTe inclusions was investigated through scanning electron microscopy, transmission electron microscopy, machine learning, and first-principles calculation. MnTe preferentially precipitated at the container mouth for sphere-like sulfides and at the interface between MnS grain boundaries and steel matrix for rod-like sulfides. The MnS/MnTe interface was semicoherent. A composition transition zone with a rock-salt structure exhibiting periodic changes existed to maintain the semicoherent interface. The critical precipitation behavior of MnTe inclusions in resulfurized steels involved three stages at varying temperatures. First, Mn(S,Te) precipitated during solidification. Second, MnTe with a rock-salt structure precipitated from Mn(S,Te). Third, MnTe with a hexagonal NiAs structure transformed from the rock-salt structure. The solubility of Te in MnS decreased with decreasing temperature. The critical precipitation behavior of MnTe inclusions in resulfurized steels was related to the MnS precipitation temperature. With the increase in MnS precipitation temperature, the critical Te/S weight ratio decreased. In consideration of the cost-effectiveness of Te addition for industrial production, the Te content in resulfurized steels should be controlled in accordance with MnS precipitation temperature and S content.
Te treatment is an effective method for modifying sulfide inclusions, and MnTe precipitation has an important effect on thermal brittleness and steel corrosion resistance. In most actual industrial applications of Te treatment, MnTe precipitation is unexpected. The critical precipitation behavior of MnTe inclusions was investigated through scanning electron microscopy, transmission electron microscopy, machine learning, and first-principles calculation. MnTe preferentially precipitated at the container mouth for sphere-like sulfides and at the interface between MnS grain boundaries and steel matrix for rod-like sulfides. The MnS/MnTe interface was semicoherent. A composition transition zone with a rock-salt structure exhibiting periodic changes existed to maintain the semicoherent interface. The critical precipitation behavior of MnTe inclusions in resulfurized steels involved three stages at varying temperatures. First, Mn(S,Te) precipitated during solidification. Second, MnTe with a rock-salt structure precipitated from Mn(S,Te). Third, MnTe with a hexagonal NiAs structure transformed from the rock-salt structure. The solubility of Te in MnS decreased with decreasing temperature. The critical precipitation behavior of MnTe inclusions in resulfurized steels was related to the MnS precipitation temperature. With the increase in MnS precipitation temperature, the critical Te/S weight ratio decreased. In consideration of the cost-effectiveness of Te addition for industrial production, the Te content in resulfurized steels should be controlled in accordance with MnS precipitation temperature and S content.
, Available online 30 June 2023,
https://doi.org/10.1007/s12613-023-2697-3
Abstract:
Flotation separation of calcite from fluorite is a challenge on low-grade fluorite flotation that limits the recovery and purity of fluorite concentrate. A new acid leaching–flotation process for fluorite is proposed in this work. This innovative process raised the fluorite’s grade to 97.26% while producing nanoscale calcium carbonate from its leachate, which contained plenty of calcium ions. On the production of nanoscale calcium carbonate, the impacts of concentration, temperature, and titration rate were examined. By modifying the process conditions and utilizing crystal conditioning agents, calcite-type and amorphous calcium carbonates with corresponding particle sizes of 1.823 and 1.511 μm were produced. The influence of the impurity ions Mn2+, Mg2+, and Fe3+ was demonstrated to reduce the particle size of nanoscale calcium carbonate and make crystal shape easier to manage in the fluorite leach solution system compared with the calcium chloride solution. The combination of the acid leaching–flotation process and the nanoscale calcium carbonate preparation method improved the grade of fluorite while recovering calcite resources, thus presenting a novel idea for the effective and clean usage of low-quality fluorite resources with embedded microfine particles.
Flotation separation of calcite from fluorite is a challenge on low-grade fluorite flotation that limits the recovery and purity of fluorite concentrate. A new acid leaching–flotation process for fluorite is proposed in this work. This innovative process raised the fluorite’s grade to 97.26% while producing nanoscale calcium carbonate from its leachate, which contained plenty of calcium ions. On the production of nanoscale calcium carbonate, the impacts of concentration, temperature, and titration rate were examined. By modifying the process conditions and utilizing crystal conditioning agents, calcite-type and amorphous calcium carbonates with corresponding particle sizes of 1.823 and 1.511 μm were produced. The influence of the impurity ions Mn2+, Mg2+, and Fe3+ was demonstrated to reduce the particle size of nanoscale calcium carbonate and make crystal shape easier to manage in the fluorite leach solution system compared with the calcium chloride solution. The combination of the acid leaching–flotation process and the nanoscale calcium carbonate preparation method improved the grade of fluorite while recovering calcite resources, thus presenting a novel idea for the effective and clean usage of low-quality fluorite resources with embedded microfine particles.
, Available online 19 March 2024,
https://doi.org/10.1007/s12613-024-2884-x
Abstract:
Short-range ordering (SRO) is one of the most important structural features of high entropy alloys (HEAs). However, the chemical and structural analyses of SROs are very difficult due to their small size, complexed compositions, and varied locations. Transmission electron microscopy (TEM) as well as its aberration correction techniques are powerful for characterizing SROs in these compositionally complex alloys. In this short communication, we summarized recent progresses regarding characterization of SROs using TEM in the field of HEAs. By using advanced TEM techniques, not only the existence of SROs was confirmed, but also the effect of SROs on the deformation mechanism was clarified. Moreover, the perspective related to application of TEM techniques in HEAs are also discussed.
Short-range ordering (SRO) is one of the most important structural features of high entropy alloys (HEAs). However, the chemical and structural analyses of SROs are very difficult due to their small size, complexed compositions, and varied locations. Transmission electron microscopy (TEM) as well as its aberration correction techniques are powerful for characterizing SROs in these compositionally complex alloys. In this short communication, we summarized recent progresses regarding characterization of SROs using TEM in the field of HEAs. By using advanced TEM techniques, not only the existence of SROs was confirmed, but also the effect of SROs on the deformation mechanism was clarified. Moreover, the perspective related to application of TEM techniques in HEAs are also discussed.
, Available online 19 February 2024,
https://doi.org/10.1007/s12613-024-2854-3
Abstract:
Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO2 emissions in the ironmaking process. However, hydrogen-enriched reduction produces large amounts of H2O, which places new demands on coke quality in a blast furnace. In a hydrogen-rich blast furnace, the presence of H2O promotes the solution loss reaction. This result improves the reactivity of coke, which is 20%–30% higher in a pure H2O atmosphere than in a pure CO2 atmosphere. The activation energy range is 110–300 kJ/mol between coke and CO2 and 80–170 kJ/mol between coke and H2O. CO2 and H2O are shown to have different effects on coke degradation mechanisms. This review provides a comprehensive overview of the effect of H2O on the structure and properties of coke. By exploring the interactions between H2O and coke, several unresolved issues in the field requiring further research were identified. This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.
Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO2 emissions in the ironmaking process. However, hydrogen-enriched reduction produces large amounts of H2O, which places new demands on coke quality in a blast furnace. In a hydrogen-rich blast furnace, the presence of H2O promotes the solution loss reaction. This result improves the reactivity of coke, which is 20%–30% higher in a pure H2O atmosphere than in a pure CO2 atmosphere. The activation energy range is 110–300 kJ/mol between coke and CO2 and 80–170 kJ/mol between coke and H2O. CO2 and H2O are shown to have different effects on coke degradation mechanisms. This review provides a comprehensive overview of the effect of H2O on the structure and properties of coke. By exploring the interactions between H2O and coke, several unresolved issues in the field requiring further research were identified. This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.
, Available online 19 February 2024,
https://doi.org/10.1007/s12613-024-2853-4
Abstract:
The A2B2O7-type rare earth zirconate compounds have been considered as promising candidates for thermal barrier coating (TBC) materials because of their low sintering rate, improved phase stability, and reduced thermal conductivity in contrast with the currently used yttria-partially stabilized zirconia (YSZ) in high operating temperature environments. This review summarizes the recent progress on rare earth zirconates for TBCs that insulate high-temperature gas from hot-section components in gas turbines. Based on the first principles, molecular dynamics, and new data-driven calculation approaches, doping and high-entropy strategies have now been adopted in advanced TBC materials design. In this paper, the solid-state heat transfer mechanism of TBCs is explained from two aspects, including heat conduction over the full operating temperature range and thermal radiation at medium and high temperature. This paper also provides new insights into design considerations of adaptive TBC materials, and the challenges and potential breakthroughs are further highlighted for extreme environmental applications. Strategies for improving thermophysical performance are proposed in two approaches: defect engineering and material compositing.
The A2B2O7-type rare earth zirconate compounds have been considered as promising candidates for thermal barrier coating (TBC) materials because of their low sintering rate, improved phase stability, and reduced thermal conductivity in contrast with the currently used yttria-partially stabilized zirconia (YSZ) in high operating temperature environments. This review summarizes the recent progress on rare earth zirconates for TBCs that insulate high-temperature gas from hot-section components in gas turbines. Based on the first principles, molecular dynamics, and new data-driven calculation approaches, doping and high-entropy strategies have now been adopted in advanced TBC materials design. In this paper, the solid-state heat transfer mechanism of TBCs is explained from two aspects, including heat conduction over the full operating temperature range and thermal radiation at medium and high temperature. This paper also provides new insights into design considerations of adaptive TBC materials, and the challenges and potential breakthroughs are further highlighted for extreme environmental applications. Strategies for improving thermophysical performance are proposed in two approaches: defect engineering and material compositing.
, Available online 30 January 2024,
https://doi.org/10.1007/s12613-024-2841-8
Abstract:
Artificially controlling the solid-state precipitation in aluminum (Al) alloys is an efficient way to achieve well-performed properties, and the microalloying strategy is the most frequently adopted method for such a purpose. In this paper, recent advances in length-scale-dependent scandium (Sc) microalloying effects in Al–Cu model alloys are reviewed. In coarse-grained Al–Cu alloys, the Sc-aided Cu/Sc/vacancies complexes that act as heterogeneous nuclei and Sc segregation at the θ′-Al2Cu/matrix interface that reduces interfacial energy contribute significantly to θ′ precipitation. By grain size refinement to the fine/ultrafine-grained scale, the strongly bonded Cu/Sc/vacancies complexes inhibit Cu and vacancy diffusing toward grain boundaries, promoting the desired intragranular θ′ precipitation. At nanocrystalline scale, the applied high strain producing high-density vacancies results in the formation of a large quantity of (Cu, Sc, vacancy)-rich atomic complexes with high thermal stability, outstandingly improving the strength/ductility synergy and preventing the intractable low-temperature precipitation. This review recommends the use of microalloying technology to modify the precipitation behaviors toward better combined mechanical properties and thermal stability in Al alloys.
Artificially controlling the solid-state precipitation in aluminum (Al) alloys is an efficient way to achieve well-performed properties, and the microalloying strategy is the most frequently adopted method for such a purpose. In this paper, recent advances in length-scale-dependent scandium (Sc) microalloying effects in Al–Cu model alloys are reviewed. In coarse-grained Al–Cu alloys, the Sc-aided Cu/Sc/vacancies complexes that act as heterogeneous nuclei and Sc segregation at the θ′-Al2Cu/matrix interface that reduces interfacial energy contribute significantly to θ′ precipitation. By grain size refinement to the fine/ultrafine-grained scale, the strongly bonded Cu/Sc/vacancies complexes inhibit Cu and vacancy diffusing toward grain boundaries, promoting the desired intragranular θ′ precipitation. At nanocrystalline scale, the applied high strain producing high-density vacancies results in the formation of a large quantity of (Cu, Sc, vacancy)-rich atomic complexes with high thermal stability, outstandingly improving the strength/ductility synergy and preventing the intractable low-temperature precipitation. This review recommends the use of microalloying technology to modify the precipitation behaviors toward better combined mechanical properties and thermal stability in Al alloys.
, Available online 1 December 2023,
https://doi.org/10.1007/s12613-023-2798-z
Abstract:
Occasional irregular initial solidification phenomena, including stickers, deep oscillation marks, depressions, and surface cracks of strand shells in continuous casting molds, are important limitations for developing the high-efficiency continuous casting of steels. The application of mold thermal monitoring (MTM) systems, which use thermocouples to detect and respond to temperature variations in molds, has become an effective method to address irregular initial solidification phenomena. Such systems are widely applied in numerous steel companies for sticker breakout prediction. However, monitoring the surface defects of strands remains immature. Hence, in-depth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems. This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems. Furthermore, the influences of mold slag behavior on monitoring these phenomena are analyzed. Finally, the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed, and future research directions are proposed.
Occasional irregular initial solidification phenomena, including stickers, deep oscillation marks, depressions, and surface cracks of strand shells in continuous casting molds, are important limitations for developing the high-efficiency continuous casting of steels. The application of mold thermal monitoring (MTM) systems, which use thermocouples to detect and respond to temperature variations in molds, has become an effective method to address irregular initial solidification phenomena. Such systems are widely applied in numerous steel companies for sticker breakout prediction. However, monitoring the surface defects of strands remains immature. Hence, in-depth research is necessary to utilize the potential advantages and comprehensive monitoring of MTM systems. This paper summarizes what is included in the irregular initial solidification phenomena and systematically reviews the current state of research on these phenomena by the MTM systems. Furthermore, the influences of mold slag behavior on monitoring these phenomena are analyzed. Finally, the remaining problems of the formation mechanisms and investigations of irregular initial solidification phenomena are discussed, and future research directions are proposed.
, Available online 21 November 2023,
https://doi.org/10.1007/s12613-023-2786-3
Abstract:
Flocculation flotation is the most efficient method for recovering fine-grained minerals, and its essence lies in flotation and recovery of flocs. Fundamental physical characteristics of flocs are mainly determined by their apparent particle size and structure (density and morphology). Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water treatment. However, the influence of floc characteristics on flotation has not been widely studied. Based on the floc formation and flocculation flotation, this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure, summarizing the interaction between floc particle size and structure. Moreover, it thoroughly discusses the effect of floc particle size and structure on floc floatability, further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and bubbles. Thus, it is observed that floc particle size is not the only factor influencing flocculation flotation. Within the appropriate apparent particle size range, flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation, thereby resulting in enhanced flotation performance. This study aims to provide a reference for flocculation flotation, targeting the development of more efficient and refined flocculation flotation processes in the future.
Flocculation flotation is the most efficient method for recovering fine-grained minerals, and its essence lies in flotation and recovery of flocs. Fundamental physical characteristics of flocs are mainly determined by their apparent particle size and structure (density and morphology). Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water treatment. However, the influence of floc characteristics on flotation has not been widely studied. Based on the floc formation and flocculation flotation, this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure, summarizing the interaction between floc particle size and structure. Moreover, it thoroughly discusses the effect of floc particle size and structure on floc floatability, further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and bubbles. Thus, it is observed that floc particle size is not the only factor influencing flocculation flotation. Within the appropriate apparent particle size range, flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation, thereby resulting in enhanced flotation performance. This study aims to provide a reference for flocculation flotation, targeting the development of more efficient and refined flocculation flotation processes in the future.
, Available online 3 November 2023,
https://doi.org/10.1007/s12613-023-2776-5
Abstract:
Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity, high operating voltage, and simple synthesis. Cycling performance is an important criterion for evaluating the application prospects of batteries. However, facing challenges, including phase transitions, ambient stability, side reactions, and irreversible anionic oxygen activity, the cycling performance of layered oxide cathode materials still cannot meet the application requirements. Therefore, this review proposes several strategies to address these challenges. First, bulk doping is introduced from three aspects: cationic single doping, anionic single doping, and multi-ion doping. Second, homogeneous surface coating and concentration gradient modification are reviewed. In addition, methods such as mixed structure design, particle engineering, high-entropy material construction, and integrated modification are proposed. Finally, a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.
Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity, high operating voltage, and simple synthesis. Cycling performance is an important criterion for evaluating the application prospects of batteries. However, facing challenges, including phase transitions, ambient stability, side reactions, and irreversible anionic oxygen activity, the cycling performance of layered oxide cathode materials still cannot meet the application requirements. Therefore, this review proposes several strategies to address these challenges. First, bulk doping is introduced from three aspects: cationic single doping, anionic single doping, and multi-ion doping. Second, homogeneous surface coating and concentration gradient modification are reviewed. In addition, methods such as mixed structure design, particle engineering, high-entropy material construction, and integrated modification are proposed. Finally, a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.
, Available online 28 September 2023,
https://doi.org/10.1007/s12613-023-2751-1
Abstract:
Plastic instability, including both the discontinuous yielding and stress serrations, has been frequently observed during the tensile deformation of medium-Mn steels (MMnS) and has been intensively studied in recent years. Unfortunately, research results are controversial, and no consensus has been achieved regarding the topic. Here, we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS, including the morphology and stability of austenite, the feature of the phase interface, and the deformation parameters. Then, we propose a universal mechanism to explain the conflicting experimental results. We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation. Meanwhile, the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite. Strain-induced martensitic transformation, influenced by the mechanical stability of austenite grain and deformation parameters, should not be the intrinsic cause of plastic instability. However, it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations, as well as the interaction between the interstitial atoms and dislocations in austenite grains.
Plastic instability, including both the discontinuous yielding and stress serrations, has been frequently observed during the tensile deformation of medium-Mn steels (MMnS) and has been intensively studied in recent years. Unfortunately, research results are controversial, and no consensus has been achieved regarding the topic. Here, we first summarize all the possible factors that affect the yielding and flow stress serrations in MMnS, including the morphology and stability of austenite, the feature of the phase interface, and the deformation parameters. Then, we propose a universal mechanism to explain the conflicting experimental results. We conclude that the discontinuous yielding can be attributed to the lack of mobile dislocation before deformation and the rapid dislocation multiplication at the beginning of plastic deformation. Meanwhile, the results show that the stress serrations are formed due to the pinning and depinning between dislocations and interstitial atoms in austenite. Strain-induced martensitic transformation, influenced by the mechanical stability of austenite grain and deformation parameters, should not be the intrinsic cause of plastic instability. However, it can intensify or weaken the discontinuous yielding and the stress serrations by affecting the mobility and density of dislocations, as well as the interaction between the interstitial atoms and dislocations in austenite grains.
, Available online 13 September 2023,
https://doi.org/10.1007/s12613-023-2745-z
Abstract:
Compared with traditional plastic forming, ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece. This technology has a very broad application prospect in industrial manufacturing. Researchers have conducted extensive research on the ultrasonic vibration plastic forming of metals and laid a deep foundation for the development of this field. In this review, metals were classified according to their crystal structures. The effects of ultrasonic vibration on the microstructure of face-centered cubic, body-centered cubic, and hexagonal close-packed metals during plastic forming and the mechanism underlying ultrasonic vibration forming were reviewed. The main challenges and future research direction of the ultrasonic vibration plastic forming of metals were also discussed.
Compared with traditional plastic forming, ultrasonic vibration plastic forming has the advantages of reducing the forming force and improving the surface quality of the workpiece. This technology has a very broad application prospect in industrial manufacturing. Researchers have conducted extensive research on the ultrasonic vibration plastic forming of metals and laid a deep foundation for the development of this field. In this review, metals were classified according to their crystal structures. The effects of ultrasonic vibration on the microstructure of face-centered cubic, body-centered cubic, and hexagonal close-packed metals during plastic forming and the mechanism underlying ultrasonic vibration forming were reviewed. The main challenges and future research direction of the ultrasonic vibration plastic forming of metals were also discussed.
, Available online 26 August 2023,
https://doi.org/10.1007/s12613-023-2731-5
Abstract:
The laser powder bed fusion (LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest, especially in the molds industry. The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds. Thus, LPBF-processed tool steels have attracted more and more attention. The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels. This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena, the microstructural characteristics, and the mechanical/thermal properties, including tensile properties, wear resistance, and thermal properties. The microstructural characteristics are presented through a multiscale perspective, ranging from densification, meso-structure, microstructure, substructure in grains, to nanoprecipitates. Finally, a summary of tool steels and their challenges and outlooks are introduced.
The laser powder bed fusion (LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest, especially in the molds industry. The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds. Thus, LPBF-processed tool steels have attracted more and more attention. The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels. This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena, the microstructural characteristics, and the mechanical/thermal properties, including tensile properties, wear resistance, and thermal properties. The microstructural characteristics are presented through a multiscale perspective, ranging from densification, meso-structure, microstructure, substructure in grains, to nanoprecipitates. Finally, a summary of tool steels and their challenges and outlooks are introduced.
, Available online 23 February 2024,
https://doi.org/10.1007/s12613-024-2862-3
Abstract:
Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer, thereby improving photoelectrochemical performance. Recently, considerable efforts have been devoted to this endeavor. This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms, focusing on the modulation of built-in electric fields in terms of depth and orderliness. First, mechanisms and tuning strategies for built-in electric fields are explored. Then, the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth. Finally, current strategies for constructing bulk built-in electric fields in photoelectrodes are explored, and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.
Constructing a built-in electric field has emerged as a key strategy for enhancing charge separation and transfer, thereby improving photoelectrochemical performance. Recently, considerable efforts have been devoted to this endeavor. This review systematically summarizes the impact of built-in electric fields on enhancing charge separation and transfer mechanisms, focusing on the modulation of built-in electric fields in terms of depth and orderliness. First, mechanisms and tuning strategies for built-in electric fields are explored. Then, the state-of-the-art works regarding built-in electric fields for modulating charge separation and transfer are summarized and categorized according to surface and interface depth. Finally, current strategies for constructing bulk built-in electric fields in photoelectrodes are explored, and insights into future developments for enhancing charge separation and transfer in high-performance photoelectrochemical applications are provided.
, Available online 25 November 2023,
https://doi.org/10.1007/s12613-023-2794-3
Abstract:
The conversion and storage of photothermal energy using phase change materials (PCMs) represent an optimal approach for harnessing clean and sustainable solar energy. Herein, we encapsulated polyethylene glycol (PEG) in montmorillonite aerogels (3D-Mt) through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs. When used as a support matrix, 3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG. Simultaneously, 3D-Mt/PEG demonstrates outstanding shape retention, increased thermal energy storage density, and commendable thermal and chemical stability. The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating–cooling cycles. Furthermore, the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels, facilitating efficient phonon transfer. This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction. This study addresses the shortcomings of PCMs, including the issues of leakage and inadequate flame retardancy. It achieves the development and design of 3D-Mt/PEG with ultrahigh strength, superior flame retardancy, and directional heat transfer. Therefore, this work offers a design strategy for the preparation of high-performance composite PCMs. The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.
The conversion and storage of photothermal energy using phase change materials (PCMs) represent an optimal approach for harnessing clean and sustainable solar energy. Herein, we encapsulated polyethylene glycol (PEG) in montmorillonite aerogels (3D-Mt) through vacuum impregnation to prepare 3D-Mt/PEG composite PCMs. When used as a support matrix, 3D-Mt can effectively prevent PEG leakage and act as a flame-retardant barrier to reduce the flammability of PEG. Simultaneously, 3D-Mt/PEG demonstrates outstanding shape retention, increased thermal energy storage density, and commendable thermal and chemical stability. The phase transition enthalpy of 3D-Mt/PEG can reach 167.53 J/g and remains stable even after 50 heating–cooling cycles. Furthermore, the vertical sheet-like structure of 3D-Mt establishes directional heat transport channels, facilitating efficient phonon transfer. This configuration results in highly anisotropic thermal conductivities that ensure swift thermal responses and efficient heat conduction. This study addresses the shortcomings of PCMs, including the issues of leakage and inadequate flame retardancy. It achieves the development and design of 3D-Mt/PEG with ultrahigh strength, superior flame retardancy, and directional heat transfer. Therefore, this work offers a design strategy for the preparation of high-performance composite PCMs. The 3D-Mt/PEG with vertically aligned and well-ordered array structure developed in this research shows great potential for thermal management and photothermal conversion applications.
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